The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An example of friction elements affecting a fill time in an automatic transmission for a vehicle may include a clutch, a brake, etc. Each of the friction elements may be operated or may not be operated at a specific shift stage. Here, the fill time means a torque preparation time for transmission.
For example, when the shift stage is a 6 stage, the operating friction element includes an over drive clutch and a 2 and 6 stage brake and the non-operating friction element includes an under drive clutch.
The existing method for a learn control of an automatic transmission learns the fill time in consideration of the operating friction element at the time of the transmission.
That is, the existing method for a learn control of an automatic transmission applies an oil pressure to the clutch operated as the friction element at the time of the transmission and performs the fill time learn by reflecting a time corresponding to a difference between a measured value and a targeted value of a turbine RPM to an initial fill time when the clutch is combined with the gear by the applied oil pressure.
The existing method for a learn control of an automatic transmission may perform the fill time learn only at the time of the transmission depending on acceleration within a specific condition, that is, a stable turbine torque range, and therefore does not perform the fill time learn under various operation conditions, in particular, the coasting operation condition in the in gear state.
Therefore, the time required for the fill time learn may not only be long, but other problems may also occur.